Traditionally vehicle electrical systems have been tested with a carbon pile variable load tester and a voltmeter. A carbon pile load tester is a variable load tester that utilizes a pile of carbon disks as a resistive load. As the carbon disks are compressed the resistance is decreased and the current through the tester increases. Carbon pile testers are capable of applying a variable load of several hundred amps to a battery or electrical system. To test the batteries on a heavy-duty vehicle with a carbon pile load tester, each battery must be disconnected from the battery bank and tested separately. The tester is connected to the battery posts and the voltage of the battery is read. If the battery voltage is below 12.45 volts, the battery must be charged before proceeding with the test. Once it is determined that the battery has sufficient charge, a load knob on the tester is manually turned by the operator to compress the carbon discs. The carbon disks are compressed until a load of one half the rated cold cranking amps (CCA) is applied to the battery. The load is maintained for 15 seconds. After 15 seconds, the voltage of the battery is noted and the load is removed by uncompressing the carbon disks. The operator then compares the noted voltage to a pass/fail voltage obtained from a chart or graph that compensates for the temperature. Unfortunately, the accuracy of this test is dependent on the skill and care of the operator.
To test the cables and the connections in the charging or starting circuits of a heavy-duty vehicle with a carbon pile load tester, the tester is connected at the alternator or at the starter. The auxiliary voltage leads of the tester (or the leads of a separate voltmeter) are connected to the battery bank. An operator applies and adjusts a load current equal to the rated output of the alternator or the specified current draw of the starter using the variable load tester. While the current flows, the operator notes the voltage at the alternator or starter and the voltage at the battery bank. The voltage drop of the system is calculated by the operator. If the voltage drop exceeds a specified amount (e.g., 0.5 volts), the electrical system is deemed problematic and the operator must determine if the problem is in the positive or the negative leg of the electrical system. This determination is made by reconnecting the auxiliary voltage leads across the positive leg and reapplying the load. The voltage may not exceed a maximum acceptable voltage drop (e.g., 0.25 volts). The voltage may not exceed one half of the maximum acceptable voltage amount (e.g., 0.25 volts). A value exceeding one half of the maximum acceptable voltage indicates a possible defect in the positive leg. Next, the auxiliary voltage leads are connected across negative leg of the system, and the load is again applied and adjusted. The voltage across the negative leg is measured. A value exceeding one half of the maximum acceptable voltage (e.g., 0.25 volts) indicates a possible defect in the negative leg.
Before testing the alternator, the operator should test the battery or batteries, and the cables between the alternator and the battery bank. The operator should make any necessary repairs based on the outcome of these tests. When testing the alternator, the operator connects the load tester to the battery bank and while the vehicle is running, reads the voltage. The alternator should regulate the voltage between approximately 13.2 volts and 14.8 volts on a 12 volt system. If the voltage is not within the specified range, there is a problem with the alternator or the voltage regulator. If the alternator maintains the voltage within the specified range, the operator applies a carbon pile load to the system until the voltage at the batteries is about 12.6 volts. At 12.6 volts the batteries will not be collecting charge or delivering current. At this point, the operator reads the current that the tester is drawing. A DC amplifier probe can also be used to measure the total output of the alternator. If the output of the alternator is within 10% of its rated output, the alternator has passed the test.
Before an operator tests the starter, the battery or batteries, the cables to the starter from the battery bank and the magnetic switch circuit should have previously been tested and repaired. A magnetic switch is a solenoid type relay that energizes the starter solenoid on the starter when the ignition key is turned to the start position. These tests, however, often do not occur. To test the starter, the operator connects the load tester to the battery bank and monitors the voltage as the engine is cranked. The operator then applies a load to the battery bank until the voltage of the battery bank reaches the voltage that was observed while the engine was cranking. At this point, the operator calculates the current that the tester is drawing. A higher than normal current draw is indicative of a bad starter.
More recently automated testers have been introduced that make testing quicker and more reliable. These testers, however, still focus on the components of the system and not the system as a whole. Often alternators and starters that are still good are misdiagnosed and removed because of another problem in the electrical system (i.e., weak batteries, corroded/damaged cables, bad connections, or a loose belt)—this is undesirable. If these alternators and starters are under warranty they are sent back to their manufacturer under a warranty claim. The manufacturer tests the unit. Because the units are still properly functioning, the warranty is denied. High costs are incurred in this type of situation. Even after high costs are incurred, the real problem has still not been resolved.
Because many starting and charging electrical problems are progressive, a good preventative maintenance test is needed to catch and correct these problems before they cause a no-start situation. Additionally, a loose alternator belt can prevent an alternator from outputting full current by not turning the alternator at full speed. Current testers have no way of determining whether the inability of the alternator to output is due to belt slippage. Temperature affects the viscosity of engine oil and the amount of current it takes to crank a starter when the oil is cold is higher than when the oil is warm. Therefore, a system and method for testing a charging and starting system for testing the systems as a whole, for testing for alternator slippage and for testing a starter system incorporating the oil temperature is needed.
There exists diagnostic tools that connect to a data port of vehicle; these tools are often referred to as scan tools. Typically, the scan tools stand-alone and do not interface with other test equipment. Presently, J1708 or J1587 and J1939 are the protocols used with the data port. Society of Automotive Engineers (SAE) documents these protocols outline. These scan tools, however, fail to provide methods and/or systems for utilizing oil temperature during a starter test and utilizing the RPM readings in determining alternator slippage.
U.S. Pat. No. 6,650,120 to Bertness et al., U.S. Pat. No. 6,718,425 to Kramptiz, and U.S. Pat. No. 6,777,945 to Pajakowski et al., and U.S. Patent Application Publication No. 2003/0038637 to Bertness et al. describe testing charging and starting system components, but fail to test the charging and/or starting system systematically and connecting to a vehicle data port.
U.S. Pat. No. 4,375,672 to Kato et al., U.S. Pat. No. 6,029,512 to Suganuma, and U.S. Pat. No. 6,466,025 to Klang, and U.S. Application Publication No. 2003/0155772 to Scherrbacher et al. disclose testing alternators to determine whether they are good. However, these references fail to disclose a system for detecting alternator belt slippage where engine RPM is read via a vehicle data port and alternator rotation is read via an R-terminal.
U.S. Pat. No. 5,583,440 to Bisher relates to testing and running AC loads on a backup system. The '440 Bisher patent, however, fails to test a battery or bank of batteries in a vehicle.
U.S. Pat. No. 6,316,914 to Bertness relates to testing a bank of batteries using a current sensor. The '914 Bertness patent, however, fails to disclose testing a bank of batteries without the use of an inter cell current sensor.
U.S. Pat. No. 6,351,102 to Troy discloses a method and system for testing vehicular batteries. The '102 Troy patent, however, fails to disclose a method and system for testing a bank of batteries.
U.S. Pat. No. 6,759,843 to Bertness et al. relates to testing storage batteries. The '843 Bertness patent, however, does not disclose testing a vehicle's bank of batteries.